hello class to review a couple reactions that we've just been learning let's Envision what reagents we're going to use to make this transformation happen so what we see here is we have two carbons and an R Group our group two carbons and same for this one right but look at the regiochemistry here if we number these carbons one and two we see in the product here we have a oxygen atom at Carbon one carbon one carbon two whereas in this one carbon one and carbon two you see the difference there here we have a Methyl Ketone and here we have an aldehyde but we start with the same reagent so what other reagents do we add here to do this and that's the cool part here I think it's because depending on the reagent that you use determines the regiochemistry and what product you're going to get so if you want a Methyl Ketone right here then you're going to have to use acid catalyzed hydration so we have sulfuric acid some water and then we need a catalyst all right so our mercury sulfate uh species right there and that's going to give us our Ketone but remember that it actually gives us the enol which then tautomerizes to our ketone all right now how do we get the oxygen on carbon two well that's the when we use the hydroboration oxidation reaction so we can treat that this is done in stepwise two steps so we have to use our Boron species now remember there's many versions of the Boron species we can just use borane if we want like bh3 in thf looks like I might need to get a different pen let's try a different pen real quick let's see this one has a little bit more ink in it all right and so that's the hydroboration part and then step two we need to do the oxidation and we do that with peroxide that's not right H2O2 and some base something's in my eye okay some sodium hydroxide and that's going to get us to this product here right now we've already gone through the mechanism for these reactions but I just wanted to highlight how cool this is depending on the reagent tells us what kind of product we're going to get so we have formed a aldehyde so keep in your mind put this in your synthesis book where you're looking at reactions how do you make methyl ketones methyl ketones are important well that starts with a terminal alkyne how do you make aldehydes terminal alkynes with the hydrophoration oxidation reaction so put write that down how to make aldehydes how to make methyl ketones this is how you do it now we're going to jump to another reaction now called halogenation of alkynes so let's clean the board and we can jump into that reaction so in the previous chapter when we were looking at halogenation of alkenes we learned that you could take an alkene and treat it with a halogen like chlorine or bromine and you could add that halogen to the double bond so if we have something like this we have X halogen right there we would generate something like this right so we've seen that before there wait wait no no that's not how it goes let's see here yes that does so that would come I'm just double checking myself here it's like this okay you know let me double check I don't want to misspeak here this okay so that that's good so what if we had something that looked like this an internal alkyne we can do the same idea here where we'll take a halogen and when we have the halogen in excess what we're going to do is now add the halogen twice because in an alkene we have one Pi Bond and an alkyne we have two so we can add it twice so we can have something that looks like this all right where we have some halogens there and like this just like that you see how you've added it twice now but these halogens right here they have to be chlorine and bromine recall that fluorine's too explosive to Violent reacts too violently and so you can't really control it iodide is too slow and just not practical to use so the salogens are chlorine and bromine those are the two that we can use here okay um now we can also control this a little bit more by only adding one equivalent of the halogen so that should be an X so one equivalent of that so it's only going to add once and so when we do that it's going to give us a mixture here we're going to get it like this where we have the halogens adding in that manner all right and let's see if we can squeeze it in here we can have it we'll just write it a little bit smaller here we can add it on opposite sides of that double bond right there like so and based off of a steric argument okay well really it's it's really hard to say why so this one's the major and this one right here is the minor and you could argue that this one makes sense to be the uh more stable or the major product because these halogens are rather large atoms and you could use a steric argument to say hey when they're on opposite sides of that double bond there's not this steric Clash that we see right there when they're on the same side of the alkene so this is the major product now we I'm not going to go through the mechanism for this reaction right here or this one right here because there's a lot of controversy around it we don't really know exactly how the mechanism works but we do know that when we take internal alkynes and we put them here we are going to get these types of products okay so this reaction you just have to remember and memorize oceanolysis of alkynes is another one of these Reactions where we're not going to worry about the mechanism because it's just too complex slash not fully understood or there's some controversy so all we have to do is remember what the products are for this reaction but a lot of the reactions that we're going to learn we are going to need to know their mechanism because it's going to help make organic chemistry easier so if we have a internal alkyne like this and we could have let's let's designate that as like an R Prime to say hey we have two different R groups if we treat that with ozone and do that in one step in the first step and then follow that up with a second step of just adding some water like so what we're going to do is it's really quite simple we're just going to take and break that triple bond in half we're going to get two pieces so we're going to get this piece right here an r and a carbon all right so R to a carbon there and then we would have an R Prime attached to a carbon okay and then to the these carbons right here which are represented there you just simply put a double bond and that so what have we done we have went from a alkyne into a carboxylic acid and you do the same thing for the other side so we have generated carboxylic acids so put that away or put that in your file how do I make carboxylic acids ozonolysis of alkynes and so you can see we have two different uh carboxylic acids well what if you only want one carboxylic acid then Fin and alkene or the two R groups are the same and then you would get two of the same carboxylic acid so that's kind of uh if very effective right you start with one substrate and boom you get two molecules out that's a pretty slick deal so for example we could simply go like something like this and boom so when we treat this with uh ozone and water what's our product going to be well we just break it right down there we keep everything here the same so we have one two three four so I'll go one two three four one two three four and then that's attached to that carbon this one is that carbon so but that has to be turned into what carboxylic acid and we can't forget that methyl so we got that what that carboxylic acid and then this one we would have one two three four one two three four we would have to um put a double bonded o on that fourth carbon one two three four one two three four and turn that into a carboxylic acid don't forget that methyl group right here so now we have our two carboxylic acids so don't need to know the mechanism but you just need to know the products here now what if we change this up and said what if we looked at a terminal alkyne and put an H there so this is different we still break the triple bond right there and so this piece on the left right here is going to give us this carboxylic acid but we're not going to get this one what we're going to get is this carbon right here we can represent it right here so there's the carbon it gets converted into carbon dioxide and that is obviously going to be in the gas phase and that's just going to bubble out a solution so terminal alkynes do in fact generate carboxylic acids but not two carboxylic acids it only makes one and then the other piece is going to be carbon dioxide so that's the major difference between a terminal and a internal alkyne let's see how many more reactions that we have I think we only have one more that we need to uh cover and the last reaction that we want to cover and this one we're going to want to know the mechanism and understand it is alkylation of terminal alkynes so what we're going to do is take a terminal alkyne and turn it into a nucleophile it's an electron-rich attacking species and then we can take that nucleophile and do reactions with it so we'll take our nucleophile treat it with an electrophile and we can generate a new carbon-carbon Bond and whenever you form new carbon-carbon bonds organic chemists ears like what new carbon carbon Bond it's very very important so let's take a look at that reaction so in a alkylation of a terminal alkene what we're doing is we have already seen previously that we can deprotonate a terminal alkynes hydrogen by treating it with the Sodium amide all right and so that's going to give us a negatively charged species when we do that first step what's that going to look like after we do step one it's going to rip off that proton and it's going to look like that and that we can call that an alkynide an alkynide ion and now do you see that with that negative charge there it's the electron Rich so it can behave like a nucleophile now alkylation is simply saying that we are attaching a alkyl alkyl group to the molecule of Interest so if I take this alkynide electron Rich species and then in the Second Step treat the alkynide with a alkyl halide so let's say this alkyl bromide right here what's going to happen is that this is the electron Rich this carbon right here is electron poor so it's going to attack in a sn2 fashion we're going to have the alkynicum electron Rich attack sn2 style giving us our product so we would get something that looks like this and then we added one two three carbons one two three there we have alkylated the alkyne and what have we done we have formed this right here this carbon and this carbon we form that Bond right there we formed a new carbon-carbon Bond all right so this is an alkylation reaction so if we clean this up and look at it in an overall reaction here we could say something to this effect right there here's our terminal alkyne we treat it one with a very strong base that can deprotonate that and sodium amide does the trick and then you have step two where you put in a primary alkyl halide and it has to be a primary alkyl halide so it can represent it like this where X can be chlorine bromine or iodine and so primary alkyl halides or a methyl iodide or a methyl halide sorry methyl halide or a primary alkyl halide those are the ones that will do an alkylation very very efficiently so what would we get here we just formed so one two three if this is our example or I could just represent it generically with this piece right here so let's erase that top one so we can just look at it generically and then we would add our R Prime there all right so let's look at it mechanistically from start to finish okay so we can understand what's going on here okay so in our first step that's an ionic species is it not so we're going whoa one two so we have a negative charge there so that's going to come in and do a proton transfer step to make uh the uh alkynide so that's going to give us this negatively charged so that's step one and then step two right there we treat it with the alkyl halide like so that's going to come in sn2 style and we will have our alkylation event and we can specify that as an R Prime so it can distinguish and then we would have our conjugate uh our anion right there from the halogen so a pretty simple mechanism right we have a proton transfer in Step One and then in step two we have a sn2 pretty straightforward if you try to do secondary alkyl halides all right that's it I'm trying to draw that as an X that doesn't look like an X anymore now does it if we change that to let's say a secondary alkyl halide then there's competition now when alkynide is made that reaction is fine it's just the moment you add step two if that alkyl halide is secondary then you're now going to uh this is not going to behave like a base so it's going to do an elimination reaction instead of a a substitution or an sn2 so you can you definitely can't use tertiary alkyl halides right because you can't do sn2 on those that's not going to work so that that one that I drew there that's a tertiary so the moral of the story if you want to do alkylation of terminal alkynes you need a primary alkyl halide because if you don't you're going to get a mixture you're going to get the major products going to be elimination products and the minor is going to be the alkylation reaction that you want so it's just not very efficient and effective okay let's see another thing you can take acetylene now acetylene has two hydrogens on each side so acetylene can undergo alkylation but this time when you do this reaction you've got to be a little bit careful all right so let me shrink this down when you use a satellite or sorry acetylene so if we have H to H so there I'm going to just make it smaller if you want to alkylate this what you're going to do is treat it with one equivalent of the sodium amide and that's going to um promote just ripping off one of the hydrogens and then you would do step two and do your appellation event okay and so that would give us that right there but if you want if that's all you want to do great done but guess what you can do it again you could do step one you'll treat it again with one equivalent uh sodium amide here and then you will generate this species right here right there an alkynide ion and then you do step two where you can treat it with the same alkyl halide if you'd like or you could use a different one so let's use a different one and so now our product is going to look something like this not that one that's there and so we did two alkylations on our acetylene so overall what have we done we have then designed and made a internal alkyne so that's another way to make internal alkynes is taking acetylene and doing these alkylation reactions pretty slick so there's many ways to do things okay let's let's pause the video for a second make sure there's nothing that I'm missing and I think we're almost done okay class that is all the reactions that we need to know for this chapter so if you have any questions or concerns as always please reach out I'm more than happy to help